Changer devices of this kind are frequently used to achieve different operating positions in a stereomicroscope, for example to connect, couple, and/or decouple, or deflect partially or wholly one of the two optical paths for documentation, for superimposing or for measurement, regulation or monitoring purposes. In addition, suitable shutters and/or filters can be placed in one or both optical paths.
DE 196 22 357 A1 discloses a changer device of this kind for switching the operating modes of a microscope tube between the positions for viewing, recording and simultaneous viewing and recording. For this, three optical elements are provided, namely a completely reflective first element, a partly transparent second element and a compensating element for compensation of the optical distance as the third optical element. The first and second elements are fixed on separate guide carriages which are arranged to be movable relative to one another. Depending on the desired operating position the optical elements are moved into or out of the optical path by pushing them in a straight line along guide rods.
Sliding constructions of this kind are mechanically complex in design, even for a single-channel microscope tube as described in DE 196 22 357 A1 and take up considerable room in stereomicroscopy as each operating position requires two optical elements arranged in pairs, which has an unfavourable effect on the shape and handling of the tube.
WO 99/13370 A1 describes a filter changing wheel for stereo-fluorescence microscopy in which a circular disc is divided into four segments, each segment carrying a number of filters arranged side by side which can be placed in the beam path of the stereomicroscope. For example, one segment might contain three filters, two of which may be placed in the viewing path while one can be placed in the illumination path. The filter carriers which carry the filters form a segment of a circle and are interchangeable. The center point of the changing wheel in this design is located far outside the center of the stereo channels, which means that the device takes up considerable space.
Other known changer devices in stereomicroscopy are currently based on sliding mechanisms. These devices are very limited in the number of operating positions (generally two positions) and also take up considerable space.
Changer devices are also known in which four or eight elements are arranged side by side in a circle, the center of rotation of the arrangement being located in the middle between the two stereo channels, i.e. in the center of the stereobase. This does indeed achieve a more compact construction than with the linear changer devices but the number of original operating positions is restricted by the fact that for each operating position two elements have to be arranged in a circle the diameter of which corresponds to the spacing of the stereo channels.
The growing need for digital documentation, for example, by means of beam decoupling and after decoupling of the beam from the microscope for add-on modules makes it necessary to have more flexible changer devices in stereomicroscopes. A large number of different operating positions should be possible while achieving a compact structure for the changer device.